The invention concerns an athletic shoe, particularly a soccer shoe, of the type having a springy-elastic sole made of plastic, to which studs, claws or spikes are attached, preferably in an easily replaceable manner.
There have been many attempts to increase the flexibility of athletic shoe soles in the area of the ball and/or in the joint area. Thus, for example, the athletic shoe sole according to DE-GM No. 19 43 819 was provided with a flexible area which was located exclusively in the ball section and faced toward the inside of the shoe, while two parallel ribs and depressions in the sole between them ran transversely across the sole longitudinal axis. On the other hand, the ground contacting side of the sole was made level, even in the flexible area, so that this reduction in sole strength on one side ensured only a limited increase in flexibility of the sole within the flexible area. In athletic shoe soles made of springy-elastic plastic such as a polyamide, polyurethane, etc., sufficient sole flexibility cannot be achieved by the above-mentioned measure, because this type of sole material is not sufficiently elastic. In addition, the flexibility of this known athletic shoe sole is limited by the fact that it is also provided with relatively wide edge strips which have no reductions in material on either side and because, when the sole is bent, the rib edges shift into an oblique position, so that they are, in practice, subjected to bending stress and, as a result, cannot absorb the athlete's weight at the instant when he feels that he has found the firm position he was seeking.
From the DE-GM No. 19 73 891, a way is known of reducing sole strength on the contact side, in order to achieve a certain flexibility of the sole. In this design, a local reduction in the strength of the central part of the sole or in the joint area is achieved by using approximately elliptical recesses or impressions in the front part of the sole and grooves running transversely across the longitudinal axis of the sole in the joint area, the walls of which are relatively thick. Thus, when ribs are also left between the adjacent grooves or recesses, these soles are hardly suitable for practical use because of the thick-walled sole in the joint area and the resulting high weight of the shoe, as well as because of the increased risk of fracture in the joint section which is endangered by notch-shaped incisions. This is compounded by the lack of reduction in thickness in the sole edge areas, which counteract its flexibility.
These disadvantages also exist in athletic shoe soles according to DE-OS No. 20 22 974 and DE-GM No. 70 06 079. In addition, especially the transverse grooves which are part of this design become collecting spots for pebbles and other foreign objects, such as dirt particles, which prevent the relatively thick sole components from returning easily to their original position. This too is quite annoying and considerably reduces the athlete's performance.
Thus, a principal object of this invention is to develop an athletic shoe, particularly a soccer shoe of the type mentioned at the beginning, in such a way that, at least in the ball area between the fittings, a flexible area of maximum flexibility is created. The joint area connected to the front part of the sole should also be easy to bend when a gradation is executed to obtain greater flexibility in the ball area than in the adjacent front joint area.
This object is achieved in accordance with preferred embodiments of the present invention by the provision of at least one flexible area on both the insole and exposed sides of the sole having ribs formed as a continuous undulating band of wave crests and valleys.
The invention achieves, in particular, the advantage that extreme bending of the front part of the sole in the ball area and preferably also in the front joint area can occur without hindering the natural roll-away process of the foot in these sole areas and can occur uniformly over the whole width of the sole. The flexing area or areas, which are designed as an undulating band, are extremely flexible because the undulating band provides a reserve of material which makes expansion possible, i.e., it allows actual stretching or elongation of the sole in the longitudinal direction of the sole or in the direction of its radius of curvature, even if springy-elastic plastics, which by nature are non-stretchable, are used. Thus, the bending force needed for bending will be reduced to a minimum and the compressive effect on the insole will be completely or very largely avoided. The undulation of the band can be adjusted such that the gain in length resulting from stretching is so great that compression of the adjoining insole does not occur at all. Basically, the insole in the flexible area or areas can also include intermediate pieces made of a volume-compressible material to absorb enough of the remaining compressive forces that the bending process of the insole is not counteracted by unwanted additional resistance.
Due to the extraordinary flexibility of the sole in the flexible area or areas, another advantage will also be obtained, consisting in the fact that, in the bending process, all of the studs, claws or spikes in the front sole area will remain attached to the ground for a relatively long period and will then be extracted from the ground fairly quickly and virtually perpendicularly, i.e., without any nominal effort, so that damage to race tracks and turf (caused mainly by the rear studs, claws or spikes in the front sole area) will be avoided and the effort required for the break-away moment will be drastically reduced.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.